Printing an image onto a print medium such as paper for consumer and industrial use is dominated generally by laser technology and ink jet technology. Ink jet technology has become more common as ink jet printing resolution and print quality have increased. Ink jet printers typically use either thermal ink jet technology or piezoelectric technology. Even though they are more expensive to manufacture than thermal ink jets, piezoelectric ink jets are generally favored, for example, because they can use a wider variety of inks.
Piezoelectric ink jet printheads typically include a flexible diaphragm manufactured from, for example, stainless steel. Piezoelectric ink jet printheads can also include an array of piezoelectric transducers (i.e., actuators) attached to the diaphragm. Other printhead structures can include one or more laser-patterned dielectric standoff layers and a flexible printed circuit (flex circuit) or printed circuit board (PCB) electrically coupled with each transducer. A printhead can further include a body plate, an inlet/outlet plate, and an aperture plate, each of which can be manufactured from stainless steel. The aperture plate includes a plurality of nozzles (i.e., one or more openings, apertures, or jets) through which ink is dispensed during printing.
During use of a piezoelectric printhead, a voltage is applied to a piezoelectric transducer, typically through electrical connection with a flex circuit electrode electrically coupled to a voltage source, which causes the piezoelectric transducer to bend or deflect, resulting in a flexing of the diaphragm. Diaphragm flexing by the piezoelectric transducer increases pressure within an ink chamber and expels a quantity of ink from the chamber through a particular nozzle in the aperture plate. As the diaphragm returns to its relaxed (unflexed) position, it reduces pressure within the chamber and draws ink into the chamber from a main ink reservoir through an opening to replace the expelled ink.
The complex three-dimensional microfluidic channels (ink ports) for ink jet printheads can be fabricated by assembling a plurality of layers which can include a number of different materials such as one or more laser patterned polymers, etched stainless steel layers, and aluminum layers. The manufacturing process can include stacking the layers within a press and applying high pressure and temperature. A plurality of adhesive films are used to effect bonding of the material layers together. An adhesive cure cycle can require the application of the pressure and temperature on the layer stack within the press for an extended duration of time, for example two hours, to minimize delamination of the layers and premature failure of the printhead during use. The adhesives which bond the various printhead layers together are formulated for both their bonding reliability and their compatibility with solid and ultraviolet inks.